In manual transmissions, as they are used in particular in motor vehicles, the synchronising assembly serves to produce a rotationally fixed connection between a transmission shaft and a transmission gear or gear wheel arranged on the transmission shaft as idler gear. In a first step of the shifting operation, the synchronizing assembly ensures that the speed of the transmission gear to be shifted is adapted to the speed of the transmission shaft. In a second step, a rotationally fixed connection between the transmission shaft and the transmission gear then is produced. The corresponding gear then is engaged.
What is generally known are synchronizing assemblies which as essential components include a synchronizer hub, thrust pieces accommodated therein, synchronizer rings as well as a selector sleeve. Upon actuation of the selector sleeve, one of the synchronizer rings is pressed against a friction surface, which is associated with the transmission gear to be shitted, via the thrust pieces and/or via the blocking bevels. When the speed of the transmission gear is synchronized with the speed of the transmission shaft, the selector sleeve can be shifted through completely, so that it engages into a toothing associated with the transmission gear. In this way, a rotationally fixed connection is produced from the synchronizer hub to the transmission gear.
What is also known are synchronizing assemblies which instead of a synchronizer hub also employ a so-called transmitter, which generally speaking combines the function of the synchroniser hub, the thrust pieces and the selector sleeve. The basic construction of a transmission with such synchronizing assembly will be explained below with reference to FIGS. 1 to 8.
The transmission contains a transmission shaft 10 on which two transmission gears 12, 14 are arranged. The two transmission gears 12, 14 are designed as idler gears, i.e. can rotate relative to the transmission shall. To each transmission gear 12, 14 a transmission gear toothing 16 is non-rotably associated. The same is provided as internal toothing on a separate component 17 which is firmly connected with the corresponding transmission gear 12, 14.
Between the two transmission gears 12, 14 a transmitter 18 is arranged, which here is formed by a transmitter disk 20 and two clutch disks 22. The two clutch disks 22 are arranged on the one and on the other side of the transmitter disk 20 and include a clutch disk external toothing 24 as well as a clutch disk internal toothing 26. The external toothing 24 is designed complementary to the transmission gear toothing 16, and the internal toothing 26 is in engagement with a transmission shaft toothing 28. Thus, the clutch disks 22 are non-rotatably coupled with the transmission shaft 10 in circumferential direction, but can be shifted on the transmission shaft in an axial direction.
On the one and on the other side of the transmitter disk 20 a synchronizer ring 30 is arranged, which can cooperate with a friction surface 32 associated with the corresponding transmission gear 12, 14. The two synchronizer rings include several carriers 34, which extend in recesses 36 in the transmitter disk 20, and two diametrically opposed connecting tabs 38 which extend through connecting openings 40 in the transmitter disk 20 (see in particular FIG. 3). The connecting tabs 38 serve to couple the two synchronizer rings with each other in an axial direction. In the coupled condition (see FIG. 4), the free ends of the carriers 34 of the two synchronizer rings 30 closely face each other.
In each of the recesses 36 a thrust piece 42 (see in particular FIGS. 5 and 6) is arranged, which is each urged to the outside in radial direction by a spring 44. At the radially outer end of each thrust piece a pre-synchronizing surface 46 is formed, which rests against pre-synchronizing bevels 48 formed at the free ends of the earners 34 on the radially inner side (see FIG. 7). The pre-synchronizing bevels 48 of the opposed carriers 34 are aligned such that a V with large opening angle is formed, whose tip points radially to the outside.
At the carriers 34 blocking surfaces 50 are formed, which as seen in circumferential direction oppose the edges of the recess 36 in an oblique alignment. Here as well, the blocking surfaces 50 form a V at the opposed carriers 34, wherein the tip of the two Vs of the opposed carriers is directed towards the center of the recess 36.
The described synchronizing assembly operates in the following way: When a gear is to be engaged, for example the one which contains the transmission gear 14, the transmitter 18 is shifted on the transmission shaft 10 in an axial direction by a means of a shift fork (not shown) in direction of the arrow P of FIG. 1. In a first step, which is called pre-synchronization, the two synchronizer rings 30 are carried to the left by the thrust pieces 42, more exactly by the pre-synchronizing surface 46 of the thrust piece 42 engaging the left pre-synchronizing bevel 48 of the left synchronizer ring 30, so that the synchronizer ring 30 gets into frictional engagement with the friction surface 32.
The speed of the transmission shaft 10 usually does not correspond to the speed of the transmission gears so that there is a speed difference between the synchronizer ring 30 and the friction surface 32. This results in the synchronizer ring being carried along in circumferential direction (see the arrow U in FIG. 8), whereby the blocking surface 50 gets in contact with the upper edge of the recess 36 as shown in FIG. 8. Due to the oblique alignment of the blocking surface 50, there is produced a force component which prevents shifting of the transmitter disk 20 relative to the earner 34; as long as a speed difference exists, the resulting friction moment leads to the fact that the blocking surface 50 remains pressed against the edge of the recess 36. The synchronizer ring supports on the friction surface 32 and cannot be shifted further in an axial direction.
The blocking force exerted by the blocking surface 50 only decreases when the speed difference is decreased, so that the edge of the recess 36 of the transmitter disk 20 can shift the blocking surface 50, due to its oblique alignment, in circumferential direction opposite to the direction of the arrow U, which provides for shifting through the transmitter. At the same time, the thrust pieces 42 are compressed downwards by the obliquely attached pre-synchronizing bevels 48 against the action of the spring 44. The transmitter thereby can axially be shifted to such an extent that the external toothing 24 of the clutch disk 22 engages into the transmission gear toothing 16 associated with the transmission gear 14, in this way, a rotationally fixed connection between the transmission shaft 10 and the transmission gear 14 to be engaged is produced.
In contrast to the illustrated embodiment it also is sufficient when a blocking chamfer defined exactly in terms of length and angle is present only at one components for example. A complementary chamfer at the opposed component, e.g. transmitter, is advantageous for a full contact with the blocking chamfers. In principle, one of the two chamfers for example might also be omitted or be designed crowned.
For releasing the shifted gear, the transmitter 18 is shifted back into its neutral position in opposite direction, whereby the two synchronizer rings 30 also are again set back into a neutral position. In this position, the fractional engagement with the friction surfaces 32 is eliminated.
It is the object underlying the invention to develop the known synchronizing assemblies to the effect that a more compact construction is obtained.